Accept No Substitutes
by chezchuckles
Summary: a co-authored fic with jstar1382. An AU version of the Nikki Heat episode. "How could he ever settle for a generic substitute when the original graced him with her presence every day?"
1. Chapter 1

**Accept No Substitutions**

 **a co-authored Nikki Heat AU with jstar1382**

* * *

Castle stared.

Natalie Rhodes was dressed like Beckett.

No, Natalie was dressed up like Nikki Heat who was inspired by Beckett…

The character and actress became a blur in his head as they stepped into the elevator. Reality versus fantasy was a jumbled mess playing out before him.

Natalie-Heat-Beckett leaned in. "I need to feel that heat…"

Before he realized what was happening, she was on him, mouth molding against his. Castle was shocked into participating, his body moving before his mind fully caught up to his actions.

"Wa - wait, Natalie." He nudged her back, creating a safe distance between him and the actress, who seemed all too willing to act out of whatever meta fantasy his mind could conjure up. This was a bad idea. At least his hormone-sludged brain was able to conclude that fact quickly enough to allow him to sidestep as the Beckett wannabe leaned in for another kiss. "No."

Her jaw dropped. Her reaction said he might be the only person that had ever had the nerve to utter that word to her. The air was thick, her body still in too close a proximity to his. He was trying to be fair, but he was a hot-blooded male.

She blinked. "No?"

"No."

"You know who I am, right?" she scoffed, narrowing her eyes. "I mean, I need to research the role and you - this relationship is definitely part of the Nikki mystique." She tried to move closer, like a huntress on the prowl, relentless.

The four walls of the elevator car were closing in on him. He dodged her assault and jumped to the opposite side. "I get that, trust me I get that, but I can't do that to her."

"To your character?"

"No, not Nikki. I can't do that to Beckett. It's complicated and this," he said, motioning towards her body, noting her near identical appearance to his partner. "This, as great as I'm sure it would be, would just complicate things further."

Natalie rolled her eyes with a half-hearted laugh, looking entirely too similar to Beckett in all of her mannerisms for his health.

She smoothed her blouse that had wrinkled from her kiss. "I don't get it, Rick. It's just sex."

The door slid open with a ding, a welcome sound, and a sigh of relief released from his lungs.

"You're right." He offered her a parting smile, stepping off of the elevator into the lobby. "You don't get it. Goodnight, Natalie."

(...)

The idea that Natalie Rhodes was well on her way to doing exactly what Beckett had feared - steal her boyfriend and kill her in her sleep - had Kate not so much horrified as heartsick.

Castle had dropped the wig box. As if his fingers had been nerveless, as if Natalie's kiss had been so great, he hadn't been able to control himself. As if-

Why was Kate obsessing? What did she care that Natalie Rhodes was doing research?

But she did. God. It was mortifying how much she cared.

Beckett sat back in her chair and allowed herself another minute to wallow in misery, her eyes following the indicator light over the elevator as it descended to the lobby. She allowed herself one minute, and one minute only, of swallowing back the tightness in her throat, of replaying the scene in her mind (how stunned he had looked, how Natalie had knocked him off his socks, finally shut him up, and it was so hard to shut him up), and then Kate sealed it off.

Closed it down. Shut the door.

Beckett turned back to the murder board, the elements of the match-maker's life neatly plotted out on the timeline, all the salient points and pertinent details, as well as a few that weren't so vital but which might prove decisive at some later date.

Never knew with a murder. Like she'd said, it was a numbers game; she would throw things up there until something shook out.

This was her element, this was where she excelled, and it was by doing this very thing: sit at her desk and stare at the board until patterns emerged. Put in the time. Do the work.

Eventually it would pay off.

She had to believe that.

(...)

Of course, easier said than done.

Beckett's concentration was shot after all that. She had tried; she had stubbornly sat before the board and told herself that none of it mattered, but it wasn't true at all.

It mattered.

And she hated that it mattered, and she hated him for mattering, and Natalie Rhodes for seeing that it mattered and so attacking Castle on the elevator by using Kate Beckett's own appearance and body language and mannerisms and everything.

It was having Beckett without having to have Beckett, and Kate wasn't at all okay with that.

A stand-in.

A substitute.

(Cheap imitation.)

So she quit.

Beckett logged off her computer, thumbed the monitor dark, and stood up. She arranged her phone in her back pocket, pulled on her jacket, checked her holstered weapon by habit. The precinct wasn't dark by any means, but it had the air of being abandoned, as if even third shift had given up the watch.

She wasn't on call. Most of her queries wouldn't come back until tomorrow morning. She had nothing else to do here.

When she strode through the bullpen, she had a moment's hesitation at the hallway where her path divided. The elevator was one way, the stairs the other, and still the image of Natalie Rhodes pressing Rick Castle against the side of the car stuck with her.

Burned in her brain. (She tried to tell herself that was a good line for tomorrow morning when Castle walked in, jauntily, with coffee. She would be snarky and smirking, poking fun of his playboy ways, of having crossed off Ryan's Freebie Five list for himself, of anything other than how her guts rolled and her feelings were hurt.)

She headed for the stairs.

She just couldn't do the elevator right now.

Maybe not for a while.

(...)

Rick Castle sat in his car, unable to start the ignition, his mind reeling with the events of the day. His hands gripped the soft leather of his steering wheel, knuckles blanching white. After the confusing summer and the ill-fated reunion with Gina, he had thought he finally had his feelings for Beckett straight in his mind.

She wasn't interested in him and it was okay. He would rather be in her life as her partner, than not in her life at all.

Partners and best friends.

It was fine.

At least that was what he had convinced himself of, but he wasn't fooling anyone - most of all he wasn't fooling himself. Natalie Rhodes nearly mauling him in the elevator had cemented one thing and one thing only in his mind. He couldn't settle for a cheap imitation when all that his body and soul craved was the real thing.

Kate Beckett was irreplaceable. She was a walking contradiction, both hard and soft, dark and light. Perfectly imperfect, she was all he'd ever wanted.

How could he ever settle for a generic substitute when the original graced him with her presence every day?

He closed his eyes for a moment, letting out a long breath, hopelessness washing over him. He had basically given up since she'd turned down his invitation to the Hamptons, told himself to move on, stop bothering her.

But that meant the newly single Beckett had no idea he wanted her still.

On top of his silence on the issue, he could admit he'd been tongue-tied over Natalie dressing up like Nikki. Beckett wasn't blind. She had to have seen his schoolboy reaction. He had practically drooled over the actress. But it was all superficial with Natalie, not like with Beckett.

There was nothing superficial about his feelings for her.

God, what if he'd blown it today? What if the fact that he couldn't momentarily control his baser instincts had ruined his chance with Beckett? He'd said nothing in months and he'd done the exact opposite of what he truly felt. Great.

He was an idiot.

With a sigh, Castle opened his eyes, blinking the haze away. And noticed Beckett hurrying from the building in search of her car. It didn't take a novelist to see that she was visibly upset. He could guess why. To hell with subtext and dancing around the issues that hung over them, he was done with the games, he was done with silence.

Reaching for the handle, he shoved open his door and jumped out, only to have the rebound smash it against his knee. His rather girly yelp must have caught her attention, because her head jerked toward his, a startled noise from her lips.

"Castle? Wha - what are you doing here?" Her face was flushed.

"I was -" He rubbed the sharp pain of his knee, tried to meet her eyes, a smile forming on his lips. "I was looking for you. Can we go somewhere to talk?"

(...)


	2. Chapter 2

**Accept No Substitutions**

 **a co-authored Nikki Heat AU with jstar1382**

* * *

(...)

She didn't want to talk.

She wanted to slink home and lick her wounds. She wanted Natalie Rhodes to stop prowling after her. She wanted Castle to never have looked at the actress in the whole new light of Nikki Heat.

Beckett fidgeted on the sidewalk, her eyes sliding away from him and taking in the details of his car. Audi A8, dark silver, the sheen of its sleek lines winking in the darkness like the night was filled with stars.

But that was an illusion. It was just an average New York City street, oil-stained and potholed, neon and workaholics' office lights burning. The car didn't seduce her, the low and raw tone of his voice didn't seduce her.

She was already seduced.

Beckett growled to herself, finally met his gaze. He was braced for disappointment; she saw it in the set of his mouth and the shift of his eyes. It was the same look she'd seen from him time and again, when she brushed him off, turned him down, refused to consider it in the slightest.

Problem was, she had considered it. Him. She'd considered so much that she'd actually found herself saying yeah, that sounds really nice to his Hamptons invitation when she'd already had a boyfriend. She'd found herself comparing the two, Demming and Castle, comparing herself around them, with them, how Castle's invitation lit things up inside her but Demming's-

So then Josh. Rebound guy, if she was being honest with herself. (Rebound from Castle's rejection, from the numb horror of having him walk off into the sunset with Gina.)

No. Just because she was unattached, just because Demming and Josh were both history didn't mean she was jumping back into baring her soul for him when he called her name and gave her those pleading eyes.

"So… is that a no, Beckett?"

"No," she exclaimed, rousing from wariness to find Castle looking at her. She knew Castle; he was her friend no matter what. It wasn't like- "I mean, of course. Yes. We can talk."

He gestured towards the car, a question.

She hesitated but finally nodded, approached the car with a measured and confident pace. Or tried anyway. But Castle was hurrying around and opening the passenger door for her, taking her bag from her shoulder, and seeing her inside the car.

She sank into the luxurious, heated leather seat, taking slow breaths to measure her heart rate. Castle opened the back door and deposited her bag in the floorboard, and then he came around with his keys in his hand, gripping them like a stress ball.

She watched him get inside the car, settle his large frame behind the wheel. When had she ever really seen him drive? Confidence and authority were her weapons to wield and she didn't know what it meant when he did.

Because he was confident, entirely so. He pulled out into traffic smoothly from his parallel parking spot, checking his mirrors with ease, the car accelerating without a hitch. He drove an automatic, but he laid his hand on the gear shift, cradling it loosely, his knees wide apart, an elbow propped on the door sill.

He hadn't asked her where she wanted to go, hadn't checked that she was willing.

She found herself silently studying this man who suddenly seemed like a stranger to her.

He was no longer just Castle, her writer tag-along. Not the smooth-talking annoying charmer who had gotten back together with his second ex-wife just for kicks.

Why had he, really? Why Gina? They started talking and connected again and that was it? All it took for him was a little interest? Ellie Monroe whispering in his ear and he was willing to be used; Gina curling him around her finger to make him finish his novel, and he was willing. Natalie Rhodes pressing against him in an elevator and he was starstruck. She didn't understand-

Oh.

He was lonely.

The realization astonished her.

But as the streetlights bathed his face, alternating shadows with harsh fluorescents, she saw the strain of being forty and a single father and wanting more in his life. Wanting it to mean something.

Wanting what Beckett had (or what he must have thought she had, but she didn't have it any longer; it was just as empty for her now going home to her apartment).

"Josh and I broke up," she blurted out. Her words fell dumb and awkward into the companionable silence, bloated things that were now hard to avoid.

Castle looked at her.

He lifted his hand from the gearshift and settled it, very lightly, at the top of her knee. "I heard."

She turned her gaze blindly to the window and realized her eyes were stinging, her throat was closing up.

She didn't know why.

She didn't want to have missed their moment. Again.

"Where-" she choked out, swallowed roughly. "Where are we going?"

"A coffee bar I know," he said into the darkness. "It's blocks from here, but they have freshly ground beans - all fair trade." And then he looked at her like words had meaning, and he wanted to impress them upon her. "It's worth the wait."

(...)

The ride was silent the rest of the way, an odd buzz of electricity that made his skin tingle with anticipation. For the first time in a long while, they were both single and he wasn't letting an ex or doctor or detective create another unnecessary obstacle between them.

He managed to find a parking spot right outside the coffee shop, the universe, for once, cutting him a break. He shifted the car into park and cut the ignition in time to hop out and move around to help Beckett from the car. She offered him a hesitant smile, her eyes focused on the press of their palms as she stepped next to him on the sidewalk.

She was still holding his hand as they went inside.

The little cafe was surprisingly busy for this time of night, but they ordered their drinks and were able to find a small booth near the back. It was amazing how fast the baristas worked for the overwhelming number of customers sipping coffee and enjoying the atmosphere.

It was quiet enough that they could talk and not worry about others overhearing, but also not entirely removed from the acoustic guitarist near the entrance. The laid-back vibe helped break the tension.

He watched as she took the first sip of her latte, hypnotized as the liquid slid down her throat. "This is amazing, Castle," she hummed, her cheeks warming.

She was gorgeous.

"Told you." He winked at her before taking a sip from his own. He was trying to keep his cool, but sitting here with her, he felt like a nervous teenager on his first date. And this wasn't even a date.

"No need to be cocky," she said, smirking against the rim of her mug. "Though my mom always said that too. I told you so." Her darkened eyelashes flirted along the delicate skin under her eyes and he found himself lost in the sight before him. Until she caught him staring, quirking her eyebrow at him. "You wanted to talk?"

"Right. I did." He cleared his throat and opened his mouth - to nothing.

Now that he had the opportunity, the open platform to purge his conscience, all the words dried up in his throat and his mind went completely blank.

Perfect.

Apparently, he was frozen for too long because Beckett broke the silence.

"Was she a good kisser?"

The boldness of her question left him choking on his latte. All hope that she hadn't seen Natalie's move on him was completely lost. He couldn't skate around the issue; this was why he had asked her to talk in the first place.

It was time to man up.

"She wanted me to help her research…" He tried to explain and it seemed pathetic even to himself, so he couldn't blame the scoff that he heard from across the table.

"Sounds like a line that a certain someone tried to use on me years ago," she mumbled.

"My following you around isn't anything like that." He was stammering, indignant.

"Really? You wouldn't take the opportunity to kiss me in the name of research? That's only reserved for big time actresses?" He could tell that she was trying to keep her voice light and joking, but there was a bite to her words. And then she lowered her eyes to her latte.

Was she hurt?

Were they both dancing around the same issue? Did they both want the same thing? He was tired of dancing, tired of trying to walk the tightrope of the push and pull of their partnership. Natalie had made him realize that substitutes would never be enough.

He had to just dive in.

"Kate, I told her no," he admitted.

Her head shot up, eyes wide. "You told her no?"

"I did." The surprise on her face made him bold and he reached across the table, placing his palm on top of her hand, squeezing. "I'm here now with you, aren't I?"

She bit down on her lip, trying to hide the smile he could see forming, stretching her cheeks.

"Wasn't she like your walking, talking fantasy? Nikki in the flesh?" she asked, teasing, flipping her hand over to thread her fingers through his.

"I'm done with cheap substitutes. Aren't you? I want the original. I want everything."

(...)


	3. Chapter 3

**Accept No Substitutes**

 **a co-authored Nikki Heat AU with jstar1382**

(...)

Kate stared.

She felt - in that moment - each sensation moving through her body. The heat of the mug where five of her fingers were wrapped around the ceramic, the air dragging in through her parted lips, the hard plane of the chair she sat on.

And she felt Castle's hand on top of hers on the table, the way he pressed down so that her palm was flattened and sweat made a damp ring on the wood. She felt the strength of his outright want, and she felt-

Out of control.

The rushing in her ears of her own frantic heartbeat. The thump of her pulse as it struggled in her throat. Skin too tight across her frame. Lips tingling. Eager.

Thrilling.

"Okay," she choked out. She had to stop, pressing a hand to her mouth to clear her throat, guard her words. "Yes."

The predatory look faded, the blue of his eyes softening. "Yes to what?"

He was going to make her say it. "I… I'm fed up with relationships that are dull and boring and - not even challenging. I want loud. I want something real." And then, as the satisfaction grew on his face, as the reckless brimming want surged inside her, she flipped her hand under his and hung on. "I want you."

His jaw dropped.

She relished the power for half a heartbeat, soaked in the heady wonderful thrill of it, and then she pushed forward and kissed him.

(He tasted dark. Coffee and a man at his wits' end. He tasted like a hint of cream, silky, rich; he tasted like all the things she'd promised to give up if only she could find her mother's-)

Castle's hand came up to her jaw, fingers so wide he dwarfed the side of her face, her neck, sank into her hair. He tugged and she felt the table cutting into her midsection, felt the urge to climb over it and into his lap, felt the giddy relief being quickly subsumed in need.

Her tongue. His hot breath. Her name a groan for mercy.

She jerked back, found her fist in his lapel, holding him against her. His eyes were on her mouth, drugged and stunned, stupefied. She stood up. He scrambled up after her.

She still had hold of his jacket; she was about to drag him out of a warm coffee shop and into the cold all because of a kiss? (Or because of another kiss in an elevator?)

No.

Beckett made herself release him. She sat down.

He collapsed back in his chair. She scraped her hair back off her face (remembered the feel of his hand in it, controlling the angle of her mouth, harsh, pressing her into him for deeper, more). She let out a breath, a long breath, finally met his eyes.

He was wordless.

"I'm not mauling you in a coffee shop," she muttered. He… squeaked? She tried very hard not to laugh, but it made her lips twitch in the corner and he narrowed his eyes. Oh, not laughing now. Wow. He was…

He could be quite intimidatingly male when he wanted to be. How the hell had he hidden all this power for so long? Look at his neck. His shoulders. His wide hands - those hands could hold her hips down and-

"Okay," she blurted out, shaking her head. "Okay, not this. We should - you said you wanted to talk. We need to talk. Talking is good." She sounded weak even to herself. "Oh God."

"Talk? No, I think we've both made ourselves very clear. Talking is over, Beckett. Let's get back to mauling."

She groaned, sank her head into her hands. "Castle." There had to be some kind of formula here, steps they were supposed to take. Rules to follow. There had to be an orderly progression or this was doomed. "You're not helping."

"Kate."

She stiffened at the soft call of her first name, lifted her head to look at him.

"You said you wanted challenging. This is it. This is where it happens. You either take a risk or-" His chin jerked, his jaw set, but his eyes were too much.

Too much emotion there. Too much to deny.

"Let's get out of here," she answered. "I'm done talking."

(...)

Beckett's hand was firmly gripping his, pulling him through the crowd until they stumbled onto the sidewalk. She seemed determined, focused, and he was just along for the ride. He felt more alive than he had in months, the electricity flowing from their kissing palms and shooting through his limbs.

Entirely overwhelmed by their physical connection, it took him a moment to realize they were walking in the complete opposite direction from his car.

"Not that I don't love your decisiveness, but where are we going?" he mused, his breath catching when his sight focused on the pure happiness within her expression, her lips stretching in a grin. Her eyes were wild with excitement.

"I want to go dancing."

"Dancing? Kate, stop for a minute," he gasped, bracing his hands against her shoulders and turning her toward him. "Are you okay?"

There was nothing more that he'd love to do than have the woman he called his partner wrapped up in his arms with her body pressed against his, but this was so unlike her. It was like he was in an episode of the Twilight Zone or some body-snatchers horror movie.

"Castle, I'm fine," she said, trying to soothe him, lifting her hand to squeeze his fingertips. "I saw a jazz club a block over on the drive here. Care to dance with me?"

"I'd love to, don't get me wrong. It's just so not like you; you're acting -"

"Impulsive? Figured, it's time to let my hair down, Rick." With a quick wink, she pulled her lip between her teeth, blanching the sensitive skin, earning his complete attention. He could tell she knew exactly the effect she was having on him, but it didn't stop his breath from stuttering when she leaned forward to whisper in his ear. "You wanted to see a little Cops Gone Wild, didn't you?"

"Beckett," he squeaked, his voice a couple octaves higher than normal, as a burst of laughter bellowed from her chest.

"Oh my God. You're so easy! It's a jazz club, not a strip club."

"You're mean," he whined, allowing her to pull his arm, leading him down the sidewalk.

"Come on. If you're good, maybe I'll let you see me drop my top."

He froze at her words, his jaw gaping as she looked up at him with an innocent smirk on her face. She was evil, pure evil but so damn hot.

"Not funny. So not funny…" He grumbled under his breath, following close behind the sway of her hips.

(...)

She really enjoyed the presence of him at her side. He wasn't even touching her yet, and she could feel the connection arcing between their bodies, the anticipation for more.

Jazz had been a good idea. The club was the basement level of what were mostly office suites, closed up for the night, while the red-globed lamps on the scattering of tables gave the brick and steel a sultry atmosphere.

They had drinks at the bar, and then they headed out onto the floor, joining a mix of people already moving to the rhythm. It was mostly the trumpet, the drummer going for cymbals, and a cello, and as the music wound around them, the spell was cast. Dark room, dark man looming, wide hands bracing her hips, her back, her shoulders. She slid her arms up his chest and laced her fingers behind his neck, tugging.

He kissed her with ease, jazz and smoke and heat, and it flared in her belly and down her legs. The confidence of his mouth was attractive, and though she'd had to nudge and push and promise things to get him here, she was drawn to the way he'd taken over.

He'd ordered their drinks without asking what she preferred (though of course he knew, and had gotten it right in one). He'd kept a hand at her hip or the small of her back while they'd talked jazz and compared the house band to the legends, his range of knowledge setting off a spark inside her. And now, his initiative holding her close, not letting her move that far from him, and the intimate press of his thighs to her thighs had her drugged with arousal.

She sighed into the last of his kiss, lifted her lids to connect with his gaze.

A feral lust had flared to life on his face, the blue of his eyes like headlights in a fog, and she dragged her hands back down his chest in response. Caught his belt with her fingers, tugged.

It was invitation, and he must have known, but he didn't move to leave. He simply swayed with her, his body a lazy cosine against hers. His hips, the strength of his shoulders, the look on his face that said he was content to play with her for however long they could survive it.

She swallowed roughly and let herself grind.

(...)


	4. Chapter 4

**Accept No Substitutes**

 **a co-authored Nikki Heat AU with jstar1382**

* * *

(...)

The haze from the club followed them back to her place. Every cell in his body was vitally charged and wound unbearably tight, craving release. But only at the hands of this celestial creature flush against his side.

Her body was soft and pliable in his arms, his lips tripping along the taut span of her neck. His hands were unable to resist finding a new patch of skin to touch, to map and claim as his own.

Falling into the elevator, the tension between them scorched the air as he tried to control himself in front of the other occupants. He didn't know whether to be thankful for the trendy couple who were riding up in the elevator with them, or to curse the addition of the little old woman and her cat who managed to step into the car right before the doors closed. Quite frankly, that old woman was the only reason he hadn't slammed the emergency stop button and had his way with Kate, the two thirty-somethings be damned.

Three years was a long wait.

They stumbled down the hallway, falling through her front door in a frantic tangle of limbs. Now that he knew the taste of her mouth and the touch of her skin on his fingertips, his patience was effectively shattered against the work of her tongue.

"I can't believe…" he panted against her skin, tattooing the words along the same trail his hands had forged.

"I know," she moaned.

He had wanted slow, had always dreamt of taking his time with her, but with Beckett grinding her hips into the cradle of his, he realized there would be plenty of time for slow.

Later.

Hauling her forward, Castle growled a warning and found the flare of lust in her eyes. He hoisted her up and cupped her bottom as she wrapped her legs around his waist. He was using all his strength to focus on not dropping her, but when she ground against him just like she had on the dance floor, he nearly lost it.

"Kate," he growled into her ear.

"Move faster." She nipped at his shoulder.

His mind went blank, momentarily wrapped in the hypnotic feel of Kate in his arms, so open, so vulnerable. It was maddening. Intoxicating.

There were no words for this feeling.

He managed to find his way into her room, fell onto the bed with her. The rest was a blur of zippers sliding, buttons scattering, and shirts ripping. They were past the point of elegance and nearing desperation. Neither one of them seemed able to calm the need to touch or be touched.

As if all the waiting had made him starved for her, as if every day forced to play the long game had created this voracious want.

It took all the restraint he had to pause a moment and appreciate her, as she should be, his eyes trailing down the naked slopes of her body to admire the lithe figure under him. Kate Beckett was magnificent and maddening and breathless.

Extraordinary.

"Castle. Please…"

She was begging him. She was writhing against him, and there was no way he wouldn't give her anything she wanted.

And then everything else he had left to give…

(...)

Kate Beckett woke before her alarm, overheated and clinging to the edge of the mattress. She scraped a hand over her mouth and rolled, but she met flesh.

Hot, naked flesh.

Man flesh.

(Oh, God, why was Lanie narrating in her head?)

But, mm, Castle.

She squirmed closer - he was splayed in the middle of the bed - and she put her mouth against his shoulder. Not quite a kiss. But not not one either.

She ran her fingers slowly down his arm, found his hand and played softly against his palm. He was still out cold, and she liked to think three rounds last night had no small part to play in that, but she'd really like round four before she had to shower for work.

And then round five in the shower?

Mm, wouldn't that be fun?

"Castle," she whispered. The smell of him filled her bed, sweat and sex and day-old aftershave, and to think all last night she'd been surreptitiously nudging her nose into the lapel of his jacket for this scent. "Rick."

He grunted and shifted as if to turn away from her.

Kate grinned and bared her teeth in his shoulder, worked his skin into her bite.

He yelped and stiffened, eyes flashing open.

There was absolutely nothing better than the way all that lust and adoration filled him. And spilled out until it made her a little breathless, and a lot overwhelmed by this massive, earth-shaking step they'd taken last night.

"Kate," he breathed. "Hi."

She brought her other arm between them, touched his lips with her fingers. He smiled against her, kissed the pads of her fingertips.

She dipped her chin back to his shoulder, placed her own kiss on the teeth marks she'd left. "Hi." Words escaped her.

"Good morning," he rumbled. His early-awake voice had a burr to it that made her shift on the bed, hips seeking resistance. He caught the tangle of her hair and pushed it off her neck. "You're entirely too gorgeous for six a.m."

"Oh, yeah? You're entirely too edible," she smiled.

He chuckled, still sleepy-sounding, still unable to mask the naked adoration on his face. She couldn't help leaning in and finally placing her lips on his.

She had thought to keep the kiss light, a pleasant good morning in return. But he groaned and moved over her, immediately pinning her to the mattress, his bulk impressive, arousing.

Determined.

But instead of starting where they'd left off, he stared down at her. Too tender. Too emotional. He had done that last night too, stopping to pay attention, to mark the moment.

She squirmed under him, just enough to get him moving, remind him of where he was and what the point of that particular good morning was, and then it was all she could do to hang on.

Ride him out.

(...)


	5. Chapter 5

**Accept No Substitutes**

 **a co-authored Nikki Heat AU with jstar1382**

* * *

This morning had been a pleasant surprise.

He hadn't expected Beckett to be so eager upon first waking up.

Hell, if he was being entirely honest, he had refused to allow himself to think past the warm, lithe figure cuddled along his side. Terrified that she would wake up with the taste of regret and eyes filled with worry.

But she was different.

Not bad different, but not the woman who had neatly and deliberately closed herself off to him this year. He almost couldn't comprehend how open and vulnerable she was with him.

She kissed him goodbye when he left her place, and her eyes - they were filled with something that he longed to call hope.

However, now that he was alone in his loft changing into clean clothes, all the fears that this would crumble at his feet came roaring through his thoughts. They had talked last night at the coffee shop, but had barely spoken at the jazz club, and had only whispered against each other's skin while they were tangled in her sheets.

Still, they hadn't defined what this was, what they were doing…

Castle stared at himself in the bathroom mirror and tried to button his shirt.

There weren't any labels attached to this new stage in their partnership and he couldn't decide what that meant for them. They'd just found their groove again after parting last summer, and now he couldn't bear to think about starting all over again with that awkward dance. Or worse, being relegated to the cold and lonely place outside her world, forced once more to scratch and claw his way inside. Last night had meant something; it'd been a step forward, surely.

No, there was no way it'd been a mistake.

Beckett had to feel the same.

Because after having her body against the delicate adoration of his mouth, he was addicted to the taste of her, to everything about her. The way her foot arched when he licked the sensitive patch of skin behind her ear was entirely too erotic. And he absolutely had to hear her gasp his name again, not that he'd forget anytime soon.

Every moment of their night together was ingrained in the synapses of his brain.

His memories of last night carried him out the front door, distracting him from the irritation of traffic through Midtown.

He rushed for the subway and got on a train in record time; he didn't want Kate to have another second alone to doubt him, them. With a quick stop at the coffee place near the Twelfth, he picked up her favorite latte, as usual, so he wouldn't upset their normal routines. Plus, he ought to make up for Natalie stealing yesterday's caffeine fix.

As he went through security on the ground floor, his body was buzzing with nervous energy, knees knocking, hands shaking.

He took a deep breath as the elevator door opened to the homicide floor.

This was it.

(...)

"Ah, good morning, Detective."

Kate spun on her heel and found him exiting the elevator, striding towards the bullpen with such a pleased look in his eye.

She chewed on the inside of her cheek to keep from breaking out into an entirely unprofessional grin, and she nodded to the two coffees in his hands. "Is that for me? Or the fictional version of me?"

A twitch of his lips was his response, and she plucked the coffee from his left hand - only to have him jerk it back and offer the right, a stammering no, here, this is yours.

It was kind of cute, in that awkward, clumsy way of two people wondering just how this dance was supposed to go.

She wrapped her fingers around her coffee, opened her mouth to say something without entirely knowing what would come out.

"Jenny!" a voice yelped.

And then the woman herself darted between the two of them, making Kate take a hasty step backwards, protecting her coffee. Ryan hustled after her, calling her again, begging her to talk.

She and Castle shared wide-eyed glances, a faint trickle of unease sliding down her spine.

Natalie Rhodes emerged from the elevator and Jenny huffed in disgust, shot Ryan a look that could kill, and flounced past Natalie. When Ryan tried to follow her, she shoved him off the elevator just as the doors closed.

"Ouch," Castle murmured.

"Drama-" Natalie started in, but Kate cut her off.

"What happened?"

Ryan cut his eyes to Natalie, then to Esposito, who had joined the crowd in the corridor. "Man, you should have told me I was your alibi."

"Oh, no," Castle said. "You went to ask her parents - and you didn't tell her."

"Can we - move on, please?" Ryan muttered, another glance to Natalie.

Beckett shut her mouth, unwilling to probe further when she knew it had something to do with the actress. She didn't want to bring personal attention to herself either, because she wasn't sure she could lie convincingly to these two. And she wasn't sure she wanted to lie.

She was afraid it was all over her face, like a full-sized ad had been taken out: we had sex last night.

Natalie pouted, apparently unhappy with the lack of attention. "So where are we on our honey-trapper?"

"Uh. Yeah." Beckett shook herself out of the neat little death spiral she was doing in her own head, and filled in the group on the work she'd accomplished while Castle had been changing clothes and getting her coffee.

She really hoped none of that showed on her face, but as they broke to their respective corners, and Castle chased after Ryan to help him fix the Jenny problem, Natalie Rhodes followed her like a bloodhound scenting a trail.

Beckett sat down, possessively folded her hands around her coffee.

Natalie sat, leaned in. "Can I ask you a question?"

This woman had pried into every nook and cranny of her life, and Beckett fully expected her secrets to be next. Magically pulled out of thin air or divined from Beckett's own silly sex glow, it would happen.

She braced herself. "Sure." She gulped a mouthful of coffee to give herself time to think when the question came.

"Is Castle gay?"

Kate sprayed coffee over her case file, clapping a hand to her mouth too late. "I'm sorry. What? No. No." She licked coffee from her fingers, disgusted with herself and how her cheeks burned and her hips shifted.

"Then you two are on item. And you're like, sworn to secrecy, right?"

"No, we are not-" Beckett swallowed, flung drops of coffee from her hand, scattering them on the already-stained pages. "Why are you asking?" Was Natalie trying to steal her boyfriend? Was Castle - could she even call him that? They'd said nothing at all about… about next.

Natalie sighed, slumped back in the chair. "Last night I invited him back to my place, and he said something I've never heard from a man before."

Oh, God. It had never occurred to her just how far Natalie Rhodes might have gotten before Castle's brain finally kicked in and said no.

"What - what was that?"

"No."

Beckett blinked. "No?"

"I don't get it. He's clearly into you, but you're determined not to give into these feelings you have for him. So he fantasizes about you through his writing. It's literally verbal masturbation."

"Hey, whoa, wha-" She closed her eyes, opened them, seeking help.

"I'm supposed to be doing research. Can't you just - give him permission?"

Her gaze snagged on Castle. "I - I have to. Go. Over there."

She jerked to her feet, swiping her hand off on her pants, and hurried around her desk towards the break room. Ryan had just exited, looking glum, but she didn't have time to stop. She pushed inside and grabbed Castle, hooking her arm through his and dragging him out of the all-too-visible break room.

"Wha-" He tripped and caught up to her. "Where are we going?"

"Somewhere private."

"Oh-okay."

She hauled him down the back hall, past the stairs, and around the corner. Just out of view. When she turned to him, he looked nervous but also somehow mulish, like a caught little boy, like he was going to fight to tell his side of the story-

Oh.

Fight for her.

Kate stepped into him, snagged him by the lapels of his jacket, and she yanked him into her for a kiss.

He moaned. That deep rumbling sound from this morning - and last night - and she lifted her hands to hold him there, her fingers in his hair. He gasped and took a shuddering breath, came back for another kiss, warm mouths and his tongue and his urgency meeting hers.

Someone laughed, far down the hall, and they broke as the same time, Castle staring at her lips, Beckett staring at his eyes.

"Kate."

She nodded, pushed her tongue over the place on her bottom lip where he'd worried it. He seemed to start breathing again, as if coming awake.

"Kate?"

"I know we didn't really talk about it." She smoothed a hand down his jacket, hooked a finger in his pocket. "But she'll have to come through me first if she wants to do any more damn research."

His jaw dropped.

She narrowed her eyes at him. "You're mine, Castle. My writer. My partner. Mine."

His lips drew into a slow, toe-curling smile, and he slid his arms around her waist, nudged his nose in against hers. His mouth close. "Message received, Kate Beckett. And, my dear detective, you have nothing to worry about. There is nothing like the real thing."

(...)


End file.
